eSIMs just need a data connection back to the SM-DP server and that can be done over Wi-Fi. I don't think that protocol is blocked that they talk to it, and the SM-DP vendors on the market are typically "global" providers that work with multiple operators.

EDIT: I checked myself to be sure. It's "RAM over HTTP(s)" -- "Remote Application Management" of the eSIM. GFW doesn't block HTTPS, so you should be able to get provisioned to any carrier worldwide while inside the firewall.

https://www.sharetechnote.com/html/Handbook_LTE_eSIM.html